Conventionally, in a pneumatic tire (hereinafter, referred to as tire) mounted on a passenger vehicle, for example, a method for forming a plurality of circumferential grooves in a tread has been widely used in order to ensure a water discharge performance on a wet road surface.
Further, there is known a tire in which a plurality of protrusions to be inclined relative to a tire circumferential direction are formed on a groove bottom of a circumferential groove in order to aggressively drain rainwater that has entered such a circumferential groove (for example, Patent Literature 1). According to such a tire, a spiral water flow is easily generated in the rainwater that has entered the circumferential grooves, resulting in the improvement of wet performance, such as the water discharge performance.